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Watanabe H, Kobikov Y, Nosova O, Sarkisyan D, Galatenko V, Carvalho L, Maia GH, Lukoyanov N, Lavrov I, Ossipov MH, Hallberg M, Schouenborg J, Zhang M, Bakalkin G. The Left-Right Side-Specific Neuroendocrine Signaling from Injured Brain: An Organizational Principle. FUNCTION 2024; 5:zqae013. [PMID: 38985004 PMCID: PMC11237900 DOI: 10.1093/function/zqae013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 03/06/2024] [Indexed: 07/11/2024] Open
Abstract
A neurological dogma is that the contralateral effects of brain injury are set through crossed descending neural tracts. We have recently identified a novel topographic neuroendocrine system (T-NES) that operates via a humoral pathway and mediates the left-right side-specific effects of unilateral brain lesions. In rats with completely transected thoracic spinal cords, unilateral injury to the sensorimotor cortex produced contralateral hindlimb flexion, a proxy for neurological deficit. Here, we investigated in acute experiments whether T-NES consists of left and right counterparts and whether they differ in neural and molecular mechanisms. We demonstrated that left- and right-sided hormonal signaling is differentially blocked by the δ-, κ- and µ-opioid antagonists. Left and right neurohormonal signaling differed in targeting the afferent spinal mechanisms. Bilateral deafferentation of the lumbar spinal cord abolished the hormone-mediated effects of the left-brain injury but not the right-sided lesion. The sympathetic nervous system was ruled out as a brain-to-spinal cord-signaling pathway since hindlimb responses were induced in rats with cervical spinal cord transections that were rostral to the preganglionic sympathetic neurons. Analysis of gene-gene co-expression patterns identified the left- and right-side-specific gene co-expression networks that were coordinated via the humoral pathway across the hypothalamus and lumbar spinal cord. The coordination was ipsilateral and disrupted by brain injury. These findings suggest that T-NES is bipartite and that its left and right counterparts contribute to contralateral neurological deficits through distinct neural mechanisms, and may enable ipsilateral regulation of molecular and neural processes across distant neural areas along the neuraxis.
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Affiliation(s)
- Hiroyuki Watanabe
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, SE-751 24, Sweden
- Department of Molecular Medicine, University of Southern Denmark, Odense, DK-5230, Denmark
| | - Yaromir Kobikov
- Volunteer Associate at Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, SE-751 24, Sweden
| | - Olga Nosova
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, SE-751 24, Sweden
| | - Daniil Sarkisyan
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, SE-751 24, Sweden
- Department of Immunology, Genetics and Pathology and Science for Life Laboratory, Uppsala University, Uppsala, SE-751 08, Sweden
| | | | - Liliana Carvalho
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Porto 4200-319, Portugal
| | - Gisela H Maia
- Centro de Investigação em Saúde Translacional e Biotecnologia Médica (TBIO)/Rede de Investigação em Saúde (RISE-Health), Escola Superior de Saúde, Instituto Politécnico do Porto, Porto 4200-072, Portugal
- Medibrain, Vila do Conde 4480-807, Portugal
- Brain Research Institute, Porto 4450-208, Portugal
| | - Nikolay Lukoyanov
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Porto 4200-319, Portugal
- Brain Research Institute, Porto 4450-208, Portugal
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4200-135, Portugal
| | - Igor Lavrov
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA
| | - Michael H Ossipov
- Department of Pharmacology, University of Arizona College of Medicine, Tucson, AZ 85724-5050, USA
| | - Mathias Hallberg
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, SE-751 24, Sweden
| | - Jens Schouenborg
- Neuronano Research Center, Department of Experimental Medical Science, Lund University, Lund 223 63, Sweden
| | - Mengliang Zhang
- Department of Molecular Medicine, University of Southern Denmark, Odense, DK-5230, Denmark
- Neuronano Research Center, Department of Experimental Medical Science, Lund University, Lund 223 63, Sweden
| | - Georgy Bakalkin
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, SE-751 24, Sweden
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2
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Lavaud S, Bichara C, D'Andola M, Yeh SH, Takeoka A. Two inhibitory neuronal classes govern acquisition and recall of spinal sensorimotor adaptation. Science 2024; 384:194-201. [PMID: 38603479 DOI: 10.1126/science.adf6801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 03/06/2024] [Indexed: 04/13/2024]
Abstract
Spinal circuits are central to movement adaptation, yet the mechanisms within the spinal cord responsible for acquiring and retaining behavior upon experience remain unclear. Using a simple conditioning paradigm, we found that dorsal inhibitory neurons are indispensable for adapting protective limb-withdrawal behavior by regulating the transmission of a specific set of somatosensory information to enhance the saliency of conditioning cues associated with limb position. By contrast, maintaining previously acquired motor adaptation required the ventral inhibitory Renshaw cells. Manipulating Renshaw cells does not affect the adaptation itself but flexibly alters the expression of adaptive behavior. These findings identify a circuit basis involving two distinct populations of spinal inhibitory neurons, which enables lasting sensorimotor adaptation independently from the brain.
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Affiliation(s)
- Simon Lavaud
- VIB-Neuroelectronics Research Flanders (NERF), 3001 Leuven, Belgium
- KU Leuven, Department of Neuroscience and Leuven Brain Institute, 3000 Leuven, Belgium
| | - Charlotte Bichara
- VIB-Neuroelectronics Research Flanders (NERF), 3001 Leuven, Belgium
- KU Leuven, Department of Neuroscience and Leuven Brain Institute, 3000 Leuven, Belgium
| | - Mattia D'Andola
- VIB-Neuroelectronics Research Flanders (NERF), 3001 Leuven, Belgium
- KU Leuven, Department of Neuroscience and Leuven Brain Institute, 3000 Leuven, Belgium
| | - Shu-Hao Yeh
- VIB-Neuroelectronics Research Flanders (NERF), 3001 Leuven, Belgium
- KU Leuven, Department of Neuroscience and Leuven Brain Institute, 3000 Leuven, Belgium
| | - Aya Takeoka
- VIB-Neuroelectronics Research Flanders (NERF), 3001 Leuven, Belgium
- KU Leuven, Department of Neuroscience and Leuven Brain Institute, 3000 Leuven, Belgium
- IMEC, 3001 Leuven, Belgium
- RIKEN Center for Brain Science, Laboratory for Motor Circuit Plasticity, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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3
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Grau JW, Hudson KE, Johnston DT, Partipilo SR. Updating perspectives on spinal cord function: motor coordination, timing, relational processing, and memory below the brain. Front Syst Neurosci 2024; 18:1184597. [PMID: 38444825 PMCID: PMC10912355 DOI: 10.3389/fnsys.2024.1184597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Accepted: 01/29/2024] [Indexed: 03/07/2024] Open
Abstract
Those studying neural systems within the brain have historically assumed that lower-level processes in the spinal cord act in a mechanical manner, to relay afferent signals and execute motor commands. From this view, abstracting temporal and environmental relations is the province of the brain. Here we review work conducted over the last 50 years that challenges this perspective, demonstrating that mechanisms within the spinal cord can organize coordinated behavior (stepping), induce a lasting change in how pain (nociceptive) signals are processed, abstract stimulus-stimulus (Pavlovian) and response-outcome (instrumental) relations, and infer whether stimuli occur in a random or regular manner. The mechanisms that underlie these processes depend upon signal pathways (e.g., NMDA receptor mediated plasticity) analogous to those implicated in brain-dependent learning and memory. New data show that spinal cord injury (SCI) can enable plasticity within the spinal cord by reducing the inhibitory effect of GABA. It is suggested that the signals relayed to the brain may contain information about environmental relations and that spinal cord systems can coordinate action in response to descending signals from the brain. We further suggest that the study of stimulus processing, learning, memory, and cognitive-like processing in the spinal cord can inform our views of brain function, providing an attractive model system. Most importantly, the work has revealed new avenues of treatment for those that have suffered a SCI.
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Affiliation(s)
- James W. Grau
- Lab of Dr. James Grau, Department of Psychological and Brain Sciences, Cellular and Behavioral Neuroscience, Texas A&M University, College Station, TX, United States
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Lukoyanov N, Watanabe H, Carvalho LS, Kononenko O, Sarkisyan D, Zhang M, Andersen MS, Lukoyanova EA, Galatenko V, Tonevitsky A, Bazov I, Iakovleva T, Schouenborg J, Bakalkin G. Left-right side-specific endocrine signaling complements neural pathways to mediate acute asymmetric effects of brain injury. eLife 2021; 10:e65247. [PMID: 34372969 PMCID: PMC8354641 DOI: 10.7554/elife.65247] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 07/07/2021] [Indexed: 12/14/2022] Open
Abstract
Brain injuries can interrupt descending neural pathways that convey motor commands from the cortex to spinal motoneurons. Here, we demonstrate that a unilateral injury of the hindlimb sensorimotor cortex of rats with completely transected thoracic spinal cord produces hindlimb postural asymmetry with contralateral flexion and asymmetric hindlimb withdrawal reflexes within 3 hr, as well as asymmetry in gene expression patterns in the lumbar spinal cord. The injury-induced postural effects were abolished by hypophysectomy and were mimicked by transfusion of serum from animals with brain injury. Administration of the pituitary neurohormones β-endorphin or Arg-vasopressin-induced side-specific hindlimb responses in naive animals, while antagonists of the opioid and vasopressin receptors blocked hindlimb postural asymmetry in rats with brain injury. Thus, in addition to the well-established involvement of motor pathways descending from the brain to spinal circuits, the side-specific humoral signaling may also add to postural and reflex asymmetries seen after brain injury.
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Affiliation(s)
- Nikolay Lukoyanov
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e CelularPortoPortugal
| | - Hiroyuki Watanabe
- Department of Pharmaceutical Biosciences, Uppsala UniversityUppsalaSweden
| | - Liliana S Carvalho
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e CelularPortoPortugal
| | - Olga Kononenko
- Department of Pharmaceutical Biosciences, Uppsala UniversityUppsalaSweden
| | - Daniil Sarkisyan
- Department of Pharmaceutical Biosciences, Uppsala UniversityUppsalaSweden
| | - Mengliang Zhang
- Neuronano Research Center, Department of Experimental Medical Science, Lund UniversityLundSweden
- Department of Molecular Medicine, University of Southern DenmarkOdenseDenmark
| | | | - Elena A Lukoyanova
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e CelularPortoPortugal
| | - Vladimir Galatenko
- Faculty of Mechanics and Mathematics, Lomonosov Moscow State UniversityMoscowRussian Federation
| | - Alex Tonevitsky
- Faculty of Biology and Biotechnology, National Research University Higher School of EconomicsMoscowRussian Federation
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry RASMoscowRussian Federation
| | - Igor Bazov
- Department of Pharmaceutical Biosciences, Uppsala UniversityUppsalaSweden
| | - Tatiana Iakovleva
- Department of Pharmaceutical Biosciences, Uppsala UniversityUppsalaSweden
| | - Jens Schouenborg
- Neuronano Research Center, Department of Experimental Medical Science, Lund UniversityLundSweden
| | - Georgy Bakalkin
- Department of Pharmaceutical Biosciences, Uppsala UniversityUppsalaSweden
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Watanabe H, Nosova O, Sarkisyan D, Storm Andersen M, Carvalho L, Galatenko V, Bazov I, Lukoyanov N, Maia GH, Hallberg M, Zhang M, Schouenborg J, Bakalkin G. Left-Right Side-Specific Neuropeptide Mechanism Mediates Contralateral Responses to a Unilateral Brain Injury. eNeuro 2021; 8:ENEURO.0548-20.2021. [PMID: 33903183 PMCID: PMC8152370 DOI: 10.1523/eneuro.0548-20.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 03/14/2021] [Accepted: 04/01/2021] [Indexed: 12/19/2022] Open
Abstract
Neuropeptides are implicated in control of lateralized processes in the brain. A unilateral brain injury (UBI) causes the contralesional sensorimotor deficits. To examine whether opioid neuropeptides mediate UBI induced asymmetric processes we compared effects of opioid antagonists on the contralesional and ipsilesional hindlimb responses to the left-sided and right-sided injury in rats. UBI induced hindlimb postural asymmetry (HL-PA) with the contralesional hindlimb flexion, and activated contralesional withdrawal reflex of extensor digitorum longus (EDL) evoked by electrical stimulation and recorded with EMG technique. No effects on the interossei (Int) and peroneaus longus (PL) were evident. The general opioid antagonist naloxone blocked postural effects, did not change EDL asymmetry while uncovered cryptic asymmetry in the PL and Int reflexes induced by UBI. Thus, the spinal opioid system may either mediate or counteract the injury effects. Strikingly, effects of selective opioid antagonists were the injury side-specific. The μ-antagonist β-funaltrexamine (FNA) and κ-antagonist nor-binaltorphimine (BNI) reduced postural asymmetry after the right but not left UBI. In contrast, the δ-antagonist naltrindole (NTI) inhibited HL-PA after the left but not right-side brain injury. The opioid gene expression and opioid peptides were lateralized in the lumbar spinal cord, and coordination between expression of the opioid and neuroplasticity-related genes was impaired by UBI that together may underlie the side-specific effects of the antagonists. We suggest that mirror-symmetric neural circuits that mediate effects of left and right brain injury on the contralesional hindlimbs are differentially controlled by the lateralized opioid system.
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Affiliation(s)
- Hiroyuki Watanabe
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden, 751 24
| | - Olga Nosova
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden, 751 24
| | - Daniil Sarkisyan
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden, 751 24
| | | | - Liliana Carvalho
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e Celular, Porto, Portugal, 4200-135
| | - Vladimir Galatenko
- Faculty of Mechanics and Mathematics, Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Igor Bazov
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden, 751 24
| | - Nikolay Lukoyanov
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e Celular, Porto, Portugal, 4200-135
- Medibrain, Vila do Conde, Porto, Portugal, 4480-807
- Brain Research Institute, Porto, Portugal, 4200-135
| | - Gisela H Maia
- Medibrain, Vila do Conde, Porto, Portugal, 4480-807
- Brain Research Institute, Porto, Portugal, 4200-135
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e Celular, Porto, Portugal, 4200-135
| | - Mathias Hallberg
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden, 751 24
| | - Mengliang Zhang
- Department of Molecular Medicine, University of Southern Denmark, Odense, Denmark, 5230
- Neuronano Research Center, Department of Experimental Medical Science, Lund University, Lund, Sweden, 223 81
| | - Jens Schouenborg
- Neuronano Research Center, Department of Experimental Medical Science, Lund University, Lund, Sweden, 223 81
| | - Georgy Bakalkin
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden, 751 24
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6
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Hoy KC, Strain MM, Turtle JD, Lee KH, Huie JR, Hartman JJ, Tarbet MM, Harlow ML, Magnuson DSK, Grau JW. Evidence That the Central Nervous System Can Induce a Modification at the Neuromuscular Junction That Contributes to the Maintenance of a Behavioral Response. J Neurosci 2020; 40:9186-9209. [PMID: 33097637 PMCID: PMC7687054 DOI: 10.1523/jneurosci.2683-19.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 11/21/2022] Open
Abstract
Neurons within the spinal cord are sensitive to environmental relations and can bring about a behavioral modification without input from the brain. For example, rats that have undergone a thoracic (T2) transection can learn to maintain a hind leg in a flexed position to minimize exposure to a noxious electrical stimulation (shock). Inactivating neurons within the spinal cord with lidocaine, or cutting communication between the spinal cord and the periphery (sciatic transection), eliminates the capacity to learn, which implies that it depends on spinal neurons. Here we show that these manipulations have no effect on the maintenance of the learned response, which implicates a peripheral process. EMG showed that learning augments the muscular response evoked by motoneuron output and that this effect survives a sciatic transection. Quantitative fluorescent imaging revealed that training brings about an increase in the area and intensity of ACh receptor labeling at the neuromuscular junction (NMJ). It is hypothesized that efferent motoneuron output, in conjunction with electrical stimulation of the tibialis anterior muscle, strengthens the connection at the NMJ in a Hebbian manner. Supporting this, paired stimulation of the efferent nerve and tibialis anterior generated an increase in flexion duration and augmented the evoked electrical response without input from the spinal cord. Evidence is presented that glutamatergic signaling contributes to plasticity at the NMJ. Labeling for vesicular glutamate transporter is evident at the motor endplate. Intramuscular application of an NMDAR antagonist blocked the acquisition/maintenance of the learned response and the strengthening of the evoked electrical response.SIGNIFICANCE STATEMENT The neuromuscular junction (NMJ) is designed to faithfully elicit a muscular contraction in response to neural input. From this perspective, encoding environmental relations (learning) and the maintenance of a behavioral modification over time (memory) are assumed to reflect only modifications upstream from the NMJ, within the CNS. The current results challenge this view. Rats were trained to maintain a hind leg in a flexed position to avoid noxious stimulation. As expected, treatments that inhibit activity within the CNS, or disrupt peripheral communication, prevented learning. These manipulations did not affect the maintenance of the acquired response. The results imply that a peripheral modification at the NMJ contributes to the maintenance of the learned response.
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Affiliation(s)
- Kevin C Hoy
- Case Comprehensive Cancer Center/Case Western Reserve School of Medicine, Cleveland, Ohio 44106
| | - Misty M Strain
- U.S. Army Institute of Surgical Research, JBSA Fort Sam Houston, Houston, Texas 78234
| | - Joel D Turtle
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Kuan H Lee
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - J Russell Huie
- Department of Neuroscience, University of California San Francisco, San Francisco, California 94110
| | - John J Hartman
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Megan M Tarbet
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Mark L Harlow
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - David S K Magnuson
- Department of Neurological Surgery, University of Louisville, Louisville, Kentucky 40202
| | - James W Grau
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
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Grau JW, Baine RE, Bean PA, Davis JA, Fauss GN, Henwood MK, Hudson KE, Johnston DT, Tarbet MM, Strain MM. Learning to promote recovery after spinal cord injury. Exp Neurol 2020; 330:113334. [PMID: 32353465 PMCID: PMC7282951 DOI: 10.1016/j.expneurol.2020.113334] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 04/19/2020] [Accepted: 04/26/2020] [Indexed: 02/06/2023]
Abstract
The present review explores the concept of learning within the context of neurorehabilitation after spinal cord injury (SCI). The aim of physical therapy and neurorehabilitation is to bring about a lasting change in function-to encourage learning. Traditionally, it was assumed that the adult spinal cord is hardwired-immutable and incapable of learning. Research has shown that neurons within the lower (lumbosacral) spinal cord can support learning after communication with the brain has been disrupted by means of a thoracic transection. Noxious stimulation can sensitize nociceptive circuits within the spinal cord, engaging signal pathways analogous to those implicated in brain-dependent learning and memory. After a spinal contusion injury, pain input can fuel hemorrhage, increase the area of tissue loss (secondary injury), and undermine long-term recovery. Neurons within the spinal cord are sensitive to environmental relations. This learning has a metaplastic effect that counters neural over-excitation and promotes adaptive learning through an up-regulation of brain-derived neurotrophic factor (BDNF). Exposure to rhythmic stimulation, treadmill training, and cycling also enhances the expression of BDNF and counters the development of nociceptive sensitization. SCI appears to enable plastic potential within the spinal cord by down-regulating the Cl- co-transporter KCC2, which reduces GABAergic inhibition. This enables learning, but also fuels over-excitation and nociceptive sensitization. Pairing epidural stimulation with activation of motor pathways also promotes recovery after SCI. Stimulating motoneurons in response to activity within the motor cortex, or a targeted muscle, has a similar effect. It is suggested that a neurofunctionalist approach can foster the discovery of processes that impact spinal function and how they may be harnessed to foster recovery after SCI.
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Affiliation(s)
- James W Grau
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA.
| | - Rachel E Baine
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Paris A Bean
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Jacob A Davis
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Gizelle N Fauss
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Melissa K Henwood
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Kelsey E Hudson
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - David T Johnston
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Megan M Tarbet
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Misty M Strain
- Battlefield Pain Research, U.S. Army Institute of Surgical Research, 3698 Chambers Pass, BHT-1, BSA Fort Sam Houston, TX 78234, USA
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Zhang M, Watanabe H, Sarkisyan D, Andersen MS, Nosova O, Galatenko V, Carvalho L, Lukoyanov N, Thelin J, Schouenborg J, Bakalkin G. Hindlimb motor responses to unilateral brain injury: spinal cord encoding and left-right asymmetry. Brain Commun 2020; 2:fcaa055. [PMID: 32954305 PMCID: PMC7425521 DOI: 10.1093/braincomms/fcaa055] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 04/02/2020] [Accepted: 04/07/2020] [Indexed: 12/26/2022] Open
Abstract
Mechanisms of motor deficits (e.g. hemiparesis and hemiplegia) secondary to stroke and traumatic brain injury remain poorly understood. In early animal studies, a unilateral lesion to the cerebellum produced postural asymmetry with ipsilateral hindlimb flexion that was retained after complete spinal cord transection. Here we demonstrate that hindlimb postural asymmetry in rats is induced by a unilateral injury of the hindlimb sensorimotor cortex, and characterize this phenomenon as a model of spinal neuroplasticity underlying asymmetric motor deficits. After cortical lesion, the asymmetry was developed due to the contralesional hindlimb flexion and persisted after decerebration and complete spinal cord transection. The asymmetry induced by the left-side brain injury was eliminated by bilateral lumbar dorsal rhizotomy, but surprisingly, the asymmetry after the right-side brain lesion was resistant to deafferentation. Pancuronium, a curare-mimetic muscle relaxant, abolished the asymmetry after the right-side lesion suggesting its dependence on the efferent drive. The contra- and ipsilesional hindlimbs displayed different musculo-articular resistance to stretch after the left but not right-side injury. The nociceptive withdrawal reflexes evoked by electrical stimulation and recorded with EMG technique were different between the left and right hindlimbs in the spinalized decerebrate rats. On this asymmetric background, a brain injury resulted in greater reflex activation on the contra- versus ipsilesional side; the difference between the limbs was higher after the right-side brain lesion. The unilateral brain injury modified expression of neuroplasticity genes analysed as readout of plastic changes, as well as robustly impaired coordination of their expression within and between the ipsi- and contralesional halves of lumbar spinal cord; the effects were more pronounced after the left side compared to the right-side injury. Our data suggest that changes in the hindlimb posture, resistance to stretch and nociceptive withdrawal reflexes are encoded by neuroplastic processes in lumbar spinal circuits induced by a unilateral brain injury. Two mechanisms, one dependent on and one independent of afferent input may mediate asymmetric hindlimb motor responses. The latter, deafferentation resistant mechanism may be based on sustained muscle contractions which often occur in patients with central lesions and which are not evoked by afferent stimulation. The unusual feature of these mechanisms is their lateralization in the spinal cord.
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Affiliation(s)
- Mengliang Zhang
- Department of Experimental Medical Science, Neuronano Research Center, Lund University, 221 00 Lund, Sweden
- Department of Molecular Medicine, University of Southern Denmark, DK-5000 Odense, Denmark
| | - Hiroyuki Watanabe
- Department of Pharmaceutical Biosciences, Uppsala University, 751 24 Uppsala, Sweden
| | - Daniil Sarkisyan
- Department of Pharmaceutical Biosciences, Uppsala University, 751 24 Uppsala, Sweden
| | - Marlene Storm Andersen
- Department of Molecular Medicine, University of Southern Denmark, DK-5000 Odense, Denmark
| | - Olga Nosova
- Department of Pharmaceutical Biosciences, Uppsala University, 751 24 Uppsala, Sweden
| | - Vladimir Galatenko
- Faculty of Mechanics and Mathematics, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Liliana Carvalho
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e Celular, 4200-319 Porto, Portugal
| | - Nikolay Lukoyanov
- Departamento de Biomedicina da Faculdade de Medicina da Universidade do Porto, Instituto de Investigação e Inovação em Saúde, Instituto de Biologia Molecular e Celular, 4200-319 Porto, Portugal
| | - Jonas Thelin
- Department of Experimental Medical Science, Neuronano Research Center, Lund University, 221 00 Lund, Sweden
| | - Jens Schouenborg
- Department of Experimental Medical Science, Neuronano Research Center, Lund University, 221 00 Lund, Sweden
| | - Georgy Bakalkin
- Department of Pharmaceutical Biosciences, Uppsala University, 751 24 Uppsala, Sweden
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9
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Brumley MR, Strain MM, Devine N, Bozeman AL. The Spinal Cord, Not to Be Forgotten: the Final Common Path for Development, Training and Recovery of Motor Function. Perspect Behav Sci 2018; 41:369-393. [PMID: 31976401 DOI: 10.1007/s40614-018-00177-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Research on learning, memory, and neural plasticity has long focused on the brain. However, the spinal cord also exhibits these phenomena to a remarkable degree. Following a spinal cord injury, the isolated spinal cord in vivo can adapt to the environment and benefit from training. The amount of plasticity or recovery of function following a spinal injury often depends on the age at which the injury occurs. In this overview, we discuss learning in the spinal cord, including associative conditioning, neural mechanisms, development, and applications to clinical populations. We take an integrated approach to the spinal cord, one that combines basic and experimental information about experience-dependent learning in animal models to clinical treatment of spinal cord injuries in humans. From such an approach, an important goal is to better inform therapeutic treatments for individuals with spinal cord injuries, as well as develop a more accurate and complete account of spinal cord and behavioral functioning.
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Affiliation(s)
- Michele R Brumley
- 1Department of Psychology, Idaho State University, 921 South 8th Avenue, Stop 8112, Pocatello, ID 83209-8112 USA
| | - Misty M Strain
- 2United States Army Institute of Surgical Research, JBSA-Fort Sam Houston, San Antonio, TX USA
| | - Nancy Devine
- 3Department of Physical and Occupational Therapy, Idaho State University, Pocatello, ID USA
| | - Aimee L Bozeman
- 1Department of Psychology, Idaho State University, 921 South 8th Avenue, Stop 8112, Pocatello, ID 83209-8112 USA
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10
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Grau JW, Huang YJ. Metaplasticity within the spinal cord: Evidence brain-derived neurotrophic factor (BDNF), tumor necrosis factor (TNF), and alterations in GABA function (ionic plasticity) modulate pain and the capacity to learn. Neurobiol Learn Mem 2018; 154:121-135. [PMID: 29635030 DOI: 10.1016/j.nlm.2018.04.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 03/01/2018] [Accepted: 04/06/2018] [Indexed: 12/15/2022]
Abstract
Evidence is reviewed that behavioral training and neural injury can engage metaplastic processes that regulate adaptive potential. This issue is explored within a model system that examines how training affects the capacity to learn within the lower (lumbosacral) spinal cord. Response-contingent (controllable) stimulation applied caudal to a spinal transection induces a behavioral modification indicative of learning. This behavioral change is not observed in animals that receive stimulation in an uncontrollable manner. Exposure to uncontrollable stimulation also engages a process that disables spinal learning for 24-48 h. Controllable stimulation has the opposite effect; it engages a process that enables learning and prevents/reverses the learning deficit induced by uncontrollable stimulation. These observations suggest that a learning episode can impact the capacity to learn in future situations, providing an example of behavioral metaplasticity. The protective/restorative effect of controllable stimulation has been linked to an up-regulation of brain-derived neurotrophic factor (BDNF). The disruption of learning has been linked to the sensitization of pain (nociceptive) circuits, which is enabled by a reduction in GABA-dependent inhibition. After spinal cord injury (SCI), the co-transporter (KCC2) that regulates the outward flow of Cl- is down-regulated. This causes the intracellular concentration of Cl- to increase, reducing (and potentially reversing) the inward flow of Cl- through the GABA-A receptor. The shift in GABA function (ionic plasticity) increases neural excitability caudal to injury and sets the stage for nociceptive sensitization. The injury-induced shift in KCC2 is related to the loss of descending serotonergic (5HT) fibers that regulate plasticity within the spinal cord dorsal horn through the 5HT-1A receptor. Evidence is presented that these alterations in spinal plasticity impact pain in a brain-dependent task (place conditioning). The findings suggest that ionic plasticity can affect learning potential, shifting a neural circuit from dampened/hard-wired to excitable/plastic.
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Affiliation(s)
- James W Grau
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA.
| | - Yung-Jen Huang
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA
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11
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Grau JW, Huang YJ, Turtle JD, Strain MM, Miranda RC, Garraway SM, Hook MA. When Pain Hurts: Nociceptive Stimulation Induces a State of Maladaptive Plasticity and Impairs Recovery after Spinal Cord Injury. J Neurotrauma 2017; 34:1873-1890. [PMID: 27788626 PMCID: PMC5444485 DOI: 10.1089/neu.2016.4626] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spinal cord injury (SCI) is often accompanied by other tissue damage (polytrauma) that provides a source of pain (nociceptive) input. Recent findings are reviewed that show SCI places the caudal tissue in a vulnerable state that exaggerates the effects nociceptive stimuli and promotes the development of nociceptive sensitization. Stimulation that is both unpredictable and uncontrollable induces a form of maladaptive plasticity that enhances nociceptive sensitization and impairs spinally mediated learning. In contrast, relational learning induces a form of adaptive plasticity that counters these adverse effects. SCI sets the stage for nociceptive sensitization by disrupting serotonergic (5HT) fibers that quell overexcitation. The loss of 5HT can enhance neural excitability by reducing membrane-bound K+-Cl- cotransporter 2, a cotransporter that regulates the outward flow of Cl-. This increases the intracellular concentration of Cl-, which reduces the hyperpolarizing (inhibitory) effect of gamma-aminobutyric acid. Uncontrollable noxious stimulation also undermines the recovery of locomotor function, and increases behavioral signs of chronic pain, after a contusion injury. Nociceptive stimulation has a greater effect if experienced soon after SCI. This adverse effect has been linked to a downregulation in brain-derived neurotrophic factor and an upregulation in the cytokine, tumor necrosis factor. Noxious input enhances tissue loss at the site of injury by increasing the extent of hemorrhage and apoptotic/pyroptotic cell death. Intrathecal lidocaine blocks nociception-induced hemorrhage, cellular indices of cell death, and its adverse effect on behavioral recovery. Clinical implications are discussed.
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Affiliation(s)
- James W. Grau
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Yung-Jen Huang
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Joel D. Turtle
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Misty M. Strain
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas
| | - Rajesh C. Miranda
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, Texas
| | - Sandra M. Garraway
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Michelle A. Hook
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, Bryan, Texas
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12
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Fixed spaced stimulation restores adaptive plasticity within the spinal cord: Identifying the eliciting conditions. Physiol Behav 2017; 174:1-9. [PMID: 28238778 DOI: 10.1016/j.physbeh.2017.02.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 02/22/2017] [Indexed: 01/21/2023]
Abstract
Prior work has shown that neurons within the spinal cord are sensitive to temporal relations and that stimulus regularity impacts nociceptive processing and adaptive plasticity. Application of brief (80ms) shocks (180-900) in a variable manner induces a form of maladaptive plasticity that inhibits spinally-mediated learning and enhances nociceptive reactivity. In contrast, an extended exposure (720-900) to stimuli given at regular (fixed spaced) intervals has a restorative effect that counters nociceptive sensitization and enables learning. The present paper explores the stimulus parameters under which this therapeutic effect of fixed spaced stimulation emerges. Spinally transected rats received variably spaced stimulation (180 shocks) to the sciatic nerve at an intensity (40-V) that recruits pain (C) fibers, producing a form of maladaptive plasticity that impairs spinal learning. As previously shown, exposure to 720 fixed spaced shocks had a therapeutic effect that restored adaptive learning. This therapeutic effect was most robust at a lower shock intensity (20V) and was equally strong irrespective of pulse duration (20-80ms). A restorative effect was observed when stimuli were given at a frequency between 0.5 and 5Hz, but not at a higher (50Hz) or lower (0.05Hz) rate. The results are consistent with prior work implicating neural systems related to the central pattern generator that drives stepping behavior. Clinical implications are discussed.
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13
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Spinal Plasticity and Behavior: BDNF-Induced Neuromodulation in Uninjured and Injured Spinal Cord. Neural Plast 2016; 2016:9857201. [PMID: 27721996 PMCID: PMC5046018 DOI: 10.1155/2016/9857201] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 07/27/2016] [Accepted: 08/10/2016] [Indexed: 12/26/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophic factor family of signaling molecules. Since its discovery over three decades ago, BDNF has been identified as an important regulator of neuronal development, synaptic transmission, and cellular and synaptic plasticity and has been shown to function in the formation and maintenance of certain forms of memory. Neural plasticity that underlies learning and memory in the hippocampus shares distinct characteristics with spinal cord nociceptive plasticity. Research examining the role BDNF plays in spinal nociception and pain overwhelmingly suggests that BDNF promotes pronociceptive effects. BDNF induces synaptic facilitation and engages central sensitization-like mechanisms. Also, peripheral injury-induced neuropathic pain is often accompanied with increased spinal expression of BDNF. Research has extended to examine how spinal cord injury (SCI) influences BDNF plasticity and the effects BDNF has on sensory and motor functions after SCI. Functional recovery and adaptive plasticity after SCI are typically associated with upregulation of BDNF. Although neuropathic pain is a common consequence of SCI, the relation between BDNF and pain after SCI remains elusive. This article reviews recent literature and discusses the diverse actions of BDNF. We also highlight similarities and differences in BDNF-induced nociceptive plasticity in naïve and SCI conditions.
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Lee KH, Huang YJ, Grau JW. Learning about Time within the Spinal Cord II: Evidence that Temporal Regularity Is Encoded by a Spinal Oscillator. Front Behav Neurosci 2016; 10:14. [PMID: 26903830 PMCID: PMC4749712 DOI: 10.3389/fnbeh.2016.00014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 01/28/2016] [Indexed: 11/13/2022] Open
Abstract
How a stimulus impacts spinal cord function depends upon temporal relations. When intermittent noxious stimulation (shock) is applied and the interval between shock pulses is varied (unpredictable), it induces a lasting alteration that inhibits adaptive learning. If the same stimulus is applied in a temporally regular (predictable) manner, the capacity to learn is preserved and a protective/restorative effect is engaged that counters the adverse effect of variable stimulation. Sensitivity to temporal relations implies a capacity to encode time. This study explores how spinal neurons discriminate variable and fixed spaced stimulation. Communication with the brain was blocked by means of a spinal transection and adaptive capacity was tested using an instrumental learning task. In this task, subjects must learn to maintain a hind limb in a flexed position to minimize shock exposure. To evaluate the possibility that a distinct class of afferent fibers provide a sensory cue for regularity, we manipulated the temporal relation between shocks given to two dermatomes (leg and tail). Evidence for timing emerged when the stimuli were applied in a coherent manner across dermatomes, implying that a central (spinal) process detects regularity. Next, we show that fixed spaced stimulation has a restorative effect when half the physical stimuli are randomly omitted, as long as the stimuli remain in phase, suggesting that stimulus regularity is encoded by an internal oscillator Research suggests that the oscillator that drives the tempo of stepping depends upon neurons within the rostral lumbar (L1-L2) region. Disrupting communication with the L1-L2 tissue by means of a L3 transection eliminated the restorative effect of fixed spaced stimulation. Implications of the results for step training and rehabilitation after injury are discussed.
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Affiliation(s)
- Kuan H Lee
- Department of Neurobiology, Center for Pain Research, University of Pittsburgh School of Medicine Pittsburgh, PA, USA
| | - Yung-Jen Huang
- Department of Psychology, Cellular and Behavioral Neuroscience, Texas A&M University College Station, TX, USA
| | - James W Grau
- Department of Psychology, Cellular and Behavioral Neuroscience, Texas A&M University College Station, TX, USA
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15
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Grau JW, Huie JR, Lee KH, Hoy KC, Huang YJ, Turtle JD, Strain MM, Baumbauer KM, Miranda RM, Hook MA, Ferguson AR, Garraway SM. Metaplasticity and behavior: how training and inflammation affect plastic potential within the spinal cord and recovery after injury. Front Neural Circuits 2014; 8:100. [PMID: 25249941 PMCID: PMC4157609 DOI: 10.3389/fncir.2014.00100] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 07/31/2014] [Indexed: 12/30/2022] Open
Abstract
Research has shown that spinal circuits have the capacity to adapt in response to training, nociceptive stimulation and peripheral inflammation. These changes in neural function are mediated by physiological and neurochemical systems analogous to those that support plasticity within the hippocampus (e.g., long-term potentiation and the NMDA receptor). As observed in the hippocampus, engaging spinal circuits can have a lasting impact on plastic potential, enabling or inhibiting the capacity to learn. These effects are related to the concept of metaplasticity. Behavioral paradigms are described that induce metaplastic effects within the spinal cord. Uncontrollable/unpredictable stimulation, and peripheral inflammation, induce a form of maladaptive plasticity that inhibits spinal learning. Conversely, exposure to controllable or predictable stimulation engages a form of adaptive plasticity that counters these maladaptive effects and enables learning. Adaptive plasticity is tied to an up-regulation of brain derived neurotrophic factor (BDNF). Maladaptive plasticity is linked to processes that involve kappa opioids, the metabotropic glutamate (mGlu) receptor, glia, and the cytokine tumor necrosis factor (TNF). Uncontrollable nociceptive stimulation also impairs recovery after a spinal contusion injury and fosters the development of pain (allodynia). These adverse effects are related to an up-regulation of TNF and a down-regulation of BDNF and its receptor (TrkB). In the absence of injury, brain systems quell the sensitization of spinal circuits through descending serotonergic fibers and the serotonin 1A (5HT 1A) receptor. This protective effect is blocked by surgical anesthesia. Disconnected from the brain, intracellular Cl- concentrations increase (due to a down-regulation of the cotransporter KCC2), which causes GABA to have an excitatory effect. It is suggested that BDNF has a restorative effect because it up-regulates KCC2 and re-establishes GABA-mediated inhibition.
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Affiliation(s)
- James W Grau
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - J Russell Huie
- Department of Neurological Surgery, Brain and Spinal Injury Center, University of California San Francisco San Francisco, CA, USA
| | - Kuan H Lee
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - Kevin C Hoy
- Department of Neurosciences, MetroHealth Medical Center and Case Western Reserve University Cleveland, OH, USA
| | - Yung-Jen Huang
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - Joel D Turtle
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | - Misty M Strain
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University, College Station TX, USA
| | | | - Rajesh M Miranda
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center Bryan, TX, USA
| | - Michelle A Hook
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center Bryan, TX, USA
| | - Adam R Ferguson
- Department of Neurological Surgery, Brain and Spinal Injury Center, University of California San Francisco San Francisco, CA, USA
| | - Sandra M Garraway
- Department of Physiology, Emory University School of Medicine Atlanta, GA, USA
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16
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Learning from the spinal cord: how the study of spinal cord plasticity informs our view of learning. Neurobiol Learn Mem 2013; 108:155-71. [PMID: 23973905 DOI: 10.1016/j.nlm.2013.08.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 08/01/2013] [Accepted: 08/07/2013] [Indexed: 01/10/2023]
Abstract
The paper reviews research examining whether and how training can induce a lasting change in spinal cord function. A framework for the study of learning, and some essential issues in experimental design, are discussed. A core element involves delayed assessment under common conditions. Research has shown that brain systems can induce a lasting (memory-like) alteration in spinal function. Neurons within the lower (lumbosacral) spinal cord can also adapt when isolated from the brain by means of a thoracic transection. Using traditional learning paradigms, evidence suggests that spinal neurons support habituation and sensitization as well as Pavlovian and instrumental conditioning. At a neurobiological level, spinal systems support phenomena (e.g., long-term potentiation), and involve mechanisms (e.g., NMDA mediated plasticity, protein synthesis) implicated in brain-dependent learning and memory. Spinal learning also induces modulatory effects that alter the capacity for learning. Uncontrollable/unpredictable stimulation disables the capacity for instrumental learning and this effect has been linked to the cytokine tumor necrosis factor (TNF). Predictable/controllable stimulation enables learning and counters the adverse effects of uncontrollable stimulation through a process that depends upon brain-derived neurotrophic factor (BDNF). Finally, uncontrollable, but not controllable, nociceptive stimulation impairs recovery after a contusion injury. A process-oriented approach (neurofunctionalism) is outlined that encourages a broader view of learning phenomena.
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Ferguson AR, Huie JR, Crown ED, Baumbauer KM, Hook MA, Garraway SM, Lee KH, Hoy KC, Grau JW. Maladaptive spinal plasticity opposes spinal learning and recovery in spinal cord injury. Front Physiol 2012; 3:399. [PMID: 23087647 PMCID: PMC3468083 DOI: 10.3389/fphys.2012.00399] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 09/20/2012] [Indexed: 01/23/2023] Open
Abstract
Synaptic plasticity within the spinal cord has great potential to facilitate recovery of function after spinal cord injury (SCI). Spinal plasticity can be induced in an activity-dependent manner even without input from the brain after complete SCI. A mechanistic basis for these effects is provided by research demonstrating that spinal synapses have many of the same plasticity mechanisms that are known to underlie learning and memory in the brain. In addition, the lumbar spinal cord can sustain several forms of learning and memory, including limb-position training. However, not all spinal plasticity promotes recovery of function. Central sensitization of nociceptive (pain) pathways in the spinal cord may emerge in response to various noxious inputs, demonstrating that plasticity within the spinal cord may contribute to maladaptive pain states. In this review we discuss interactions between adaptive and maladaptive forms of activity-dependent plasticity in the spinal cord below the level of SCI. The literature demonstrates that activity-dependent plasticity within the spinal cord must be carefully tuned to promote adaptive spinal training. Prior work from our group has shown that stimulation that is delivered in a limb position-dependent manner or on a fixed interval can induce adaptive plasticity that promotes future spinal cord learning and reduces nociceptive hyper-reactivity. On the other hand, stimulation that is delivered in an unsynchronized fashion, such as randomized electrical stimulation or peripheral skin injuries, can generate maladaptive spinal plasticity that undermines future spinal cord learning, reduces recovery of locomotor function, and promotes nociceptive hyper-reactivity after SCI. We review these basic phenomena, how these findings relate to the broader spinal plasticity literature, discuss the cellular and molecular mechanisms, and finally discuss implications of these and other findings for improved rehabilitative therapies after SCI.
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Affiliation(s)
- Adam R Ferguson
- Department of Neurological Surgery, Brain and Spinal Injury Center, University of California San Francisco San Francisco, CA, USA
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18
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Hoy KC, Huie JR, Grau JW. AMPA receptor mediated behavioral plasticity in the isolated rat spinal cord. Behav Brain Res 2012; 236:319-326. [PMID: 22982187 DOI: 10.1016/j.bbr.2012.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 08/31/2012] [Accepted: 09/05/2012] [Indexed: 12/18/2022]
Abstract
Previous research has demonstrated that the spinal cord is capable of a simple form of instrumental learning. Spinally transected rats that receive shock to a hind leg in an extended position quickly learn to maintain the leg in a flexed position, reducing net shock exposure whenever that leg is flexed. Subjects that receive shock independent of leg position (uncontrollable shock) do not exhibit an increase in flexion duration and later fail to learn when tested with controllable shock (learning deficit). The present study examined the role of the ionotropic glutamate receptor α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) in spinal learning. Intrathecal application of the AMPA receptor antagonist CNQX disrupted performance of a spinal instrumental learning in a dose dependent fashion (Experiment 1). CNQX also disrupted the maintenance of the instrumental response (Experiment 2) and blocked the induction of the learning deficit (Experiment 3). Intrathecal application of the agonist AMPA had a non-monotonic effect, producing a slight facilitation of performance at a low dose and disrupting learning at a high concentration (Experiment 4). Within the dose range tested, intrathecal application of AMPA did not have a long-term effect (Experiment 5). The results suggest that AMPA-mediated transmission plays an essential role in both instrumental learning and the induction of the learning deficit.
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Affiliation(s)
- Kevin C Hoy
- Texas A&M University, College Station, TX 77843-4235, United States.
| | - J Russell Huie
- University of California, San Francisco, CA, United States
| | - James W Grau
- Texas A&M University, College Station, TX 77843-4235, United States
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Grau JW, Huie JR, Garraway SM, Hook MA, Crown ED, Baumbauer KM, Lee KH, Hoy KC, Ferguson AR. Impact of behavioral control on the processing of nociceptive stimulation. Front Physiol 2012; 3:262. [PMID: 22934018 PMCID: PMC3429038 DOI: 10.3389/fphys.2012.00262] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 06/23/2012] [Indexed: 12/24/2022] Open
Abstract
How nociceptive signals are processed within the spinal cord, and whether these signals lead to behavioral signs of neuropathic pain, depends upon their relation to other events and behavior. Our work shows that these relations can have a lasting effect on spinal plasticity, inducing a form of learning that alters the effect of subsequent nociceptive stimuli. The capacity of lower spinal systems to adapt, in the absence of brain input, is examined in spinally transected rats that receive a nociceptive shock to the tibialis anterior muscle of one hind leg. If shock is delivered whenever the leg is extended (controllable stimulation), it induces an increase in flexion duration that minimizes net shock exposure. This learning is not observed in subjects that receive the same amount of shock independent of leg position (uncontrollable stimulation). These two forms of stimulation have a lasting, and divergent, effect on subsequent learning: controllable stimulation enables learning whereas uncontrollable stimulation disables it (learning deficit). Uncontrollable stimulation also enhances mechanical reactivity. We review evidence that training with controllable stimulation engages a brain-derived neurotrophic factor (BDNF)-dependent process that can both prevent and reverse the consequences of uncontrollable shock. We relate these effects to changes in BDNF protein and TrkB signaling. Controllable stimulation is also shown to counter the effects of peripheral inflammation (from intradermal capsaicin). A model is proposed that assumes nociceptive input is gated at an early sensory stage. This gate is sensitive to current environmental relations (between proprioceptive and nociceptive input), allowing stimulation to be classified as controllable or uncontrollable. We further propose that the status of this gate is affected by past experience and that a history of uncontrollable stimulation will promote the development of neuropathic pain.
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Affiliation(s)
- James W Grau
- Cellular and Behavioral Neuroscience, Department of Psychology, Texas A&M University College Station, TX, USA
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20
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Huie JR, Baumbauer KM, Lee KH, Bresnahan JC, Beattie MS, Ferguson AR, Grau JW. Glial tumor necrosis factor alpha (TNFα) generates metaplastic inhibition of spinal learning. PLoS One 2012; 7:e39751. [PMID: 22745823 PMCID: PMC3379985 DOI: 10.1371/journal.pone.0039751] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 05/28/2012] [Indexed: 12/28/2022] Open
Abstract
Injury-induced overexpression of tumor necrosis factor alpha (TNFα) in the spinal cord can induce chronic neuroinflammation and excitotoxicity that ultimately undermines functional recovery. Here we investigate how TNFα might also act to upset spinal function by modulating spinal plasticity. Using a model of instrumental learning in the injured spinal cord, we have previously shown that peripheral intermittent stimulation can produce a plastic change in spinal plasticity (metaplasticity), resulting in the prolonged inhibition of spinal learning. We hypothesized that spinal metaplasticity may be mediated by TNFα. We found that intermittent stimulation increased protein levels in the spinal cord. Using intrathecal pharmacological manipulations, we showed TNFα to be both necessary and sufficient for the long-term inhibition of a spinal instrumental learning task. These effects were found to be dependent on glial production of TNFα and involved downstream alterations in calcium-permeable AMPA receptors. These findings suggest a crucial role for glial TNFα in undermining spinal learning, and demonstrate the therapeutic potential of inhibiting TNFα activity to rescue and restore adaptive spinal plasticity to the injured spinal cord. TNFα modulation represents a novel therapeutic target for improving rehabilitation after spinal cord injury.
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Affiliation(s)
- J. Russell Huie
- Department of Psychology, Texas A&M University, College Station, Texas, United States of America
- Brain and Spinal Injury Center, Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail: (JRH); (ARF)
| | - Kyle M. Baumbauer
- Department of Psychology, Texas A&M University, College Station, Texas, United States of America
| | - Kuan H. Lee
- Department of Psychology, Texas A&M University, College Station, Texas, United States of America
| | - Jacqueline C. Bresnahan
- Brain and Spinal Injury Center, Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States of America
| | - Michael S. Beattie
- Brain and Spinal Injury Center, Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States of America
| | - Adam R. Ferguson
- Brain and Spinal Injury Center, Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail: (JRH); (ARF)
| | - James W. Grau
- Department of Psychology, Texas A&M University, College Station, Texas, United States of America
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21
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Baumbauer KM, Grau JW. Timing in the absence of supraspinal input III: regularly spaced cutaneous stimulation prevents and reverses the spinal learning deficit produced by peripheral inflammation. Behav Neurosci 2011; 125:37-45. [PMID: 21319886 DOI: 10.1037/a0022009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In the absence of brain input, spinal systems can adapt to new environmental relations. For example, spinally transected rats given a legshock each time the leg is extended exhibit a progressive increase in flexion duration that minimizes net shock exposure, a simple form of instrumental learning. This capacity for learning is modulated by prior stimulation; both variable shock and inflammation produce a lasting inhibition of learning. An extended exposure to fixed spaced shock has no adverse effect on learning and opposes the consequences of variable shock. The present studies expand on these findings and demonstrate that fixed stimulation ameliorates the impact of peripheral inflammation. Spinally transected rats were administered 900 fixed spaced legshocks before (Experiment 1) or 1,800 legshocks after (Experiment 2) a subcutaneous hindpaw injection of capsaicin. Learning was assessed 24 hr later. Treatment with fixed shock attenuated the capsaicin-induced inhibition of learning. These findings suggest that fixed stimulation promotes adaptive plasticity and may foster recovery after injury.
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Affiliation(s)
- Kyle M Baumbauer
- Department of Psychology, Texas A&M University, College Station, TX 77843, USA.
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22
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Ferguson AR, Stück ED, Nielson JL. Syndromics: a bioinformatics approach for neurotrauma research. Transl Stroke Res 2011; 2:438-54. [PMID: 22207883 PMCID: PMC3236294 DOI: 10.1007/s12975-011-0121-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/14/2011] [Accepted: 10/18/2011] [Indexed: 12/25/2022]
Abstract
Substantial scientific progress has been made in the past 50 years in delineating many of the biological mechanisms involved in the primary and secondary injuries following trauma to the spinal cord and brain. These advances have highlighted numerous potential therapeutic approaches that may help restore function after injury. Despite these advances, bench-to-bedside translation has remained elusive. Translational testing of novel therapies requires standardized measures of function for comparison across different laboratories, paradigms, and species. Although numerous functional assessments have been developed in animal models, it remains unclear how to best integrate this information to describe the complete translational "syndrome" produced by neurotrauma. The present paper describes a multivariate statistical framework for integrating diverse neurotrauma data and reviews the few papers to date that have taken an information-intensive approach for basic neurotrauma research. We argue that these papers can be described as the seminal works of a new field that we call "syndromics", which aim to apply informatics tools to disease models to characterize the full set of mechanistic inter-relationships from multi-scale data. In the future, centralized databases of raw neurotrauma data will enable better syndromic approaches and aid future translational research, leading to more efficient testing regimens and more clinically relevant findings.
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Affiliation(s)
- Adam R. Ferguson
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, 1001 Potrero Avenue, Building 1, Room 101, San Francisco, CA 94110 USA
| | - Ellen D. Stück
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, 1001 Potrero Avenue, Building 1, Room 101, San Francisco, CA 94110 USA
| | - Jessica L. Nielson
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, 1001 Potrero Avenue, Building 1, Room 101, San Francisco, CA 94110 USA
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Huie JR, Garraway SM, Baumbauer KM, Hoy KC, Beas BS, Montgomery KS, Bizon JL, Grau JW. Brain-derived neurotrophic factor promotes adaptive plasticity within the spinal cord and mediates the beneficial effects of controllable stimulation. Neuroscience 2011; 200:74-90. [PMID: 22056599 DOI: 10.1016/j.neuroscience.2011.10.028] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Revised: 10/14/2011] [Accepted: 10/15/2011] [Indexed: 01/22/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) has been characterized as a potent modulator of neural plasticity in both the brain and spinal cord. The present experiments use an in vivo model system to demonstrate that training with controllable stimulation increases spinal BDNF expression and engages a BDNF-dependent process that promotes adaptive plasticity. Spinally transected rats administered legshock whenever one hind limb is extended (controllable stimulation) exhibit a progressive increase in flexion duration. This simple form of response-outcome (instrumental) learning is not observed when shock is given independent of leg position (uncontrollable stimulation). Uncontrollable electrical stimulation also induces a lasting effect that impairs learning for up to 48 h. Training with controllable shock can counter the adverse consequences of uncontrollable stimulation, to both prevent and reverse the learning deficit. Here it is shown that the protective and restorative effect of instrumental training depends on BDNF. Cellular assays showed that controllable stimulation increased BDNF mRNA expression and protein within the lumbar spinal cord. These changes were associated with an increase in the BDNF receptor TrkB protein within the dorsal horn. Evidence is then presented that these changes play a functional role in vivo. Application of a BDNF inhibitor (TrkB-IgG) blocked the protective effect of instrumental training. Direct (intrathecal) application of BDNF substituted for instrumental training to block both the induction and expression of the learning deficit. Uncontrollable stimulation also induced an increase in mechanical reactivity (allodynia), and this too was prevented by BDNF. TrkB-IgG blocked the restorative effect of instrumental training and intrathecal BDNF substituted for training to reverse the deficit. Taken together, these findings outline a critical role for BDNF in mediating the beneficial effects of controllable stimulation on spinal plasticity.
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Affiliation(s)
- J R Huie
- Department of Psychology, Mail Stop 4235, Texas A&M University, College Station, TX 77843, USA.
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24
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Timing in the absence of supraspinal input II: regularly spaced stimulation induces a lasting alteration in spinal function that depends on the NMDA receptor, BDNF release, and protein synthesis. J Neurosci 2009; 29:14383-93. [PMID: 19923273 DOI: 10.1523/jneurosci.3583-09.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The detection of temporal regularity allows organisms to predict the occurrence of future events. When events occur in an irregular manner, uncertainty is increased, and negative outcomes can ensue (e.g., stress). The present study shows that spinal neurons can discriminate between variable- and fixed-spaced stimulation and that the detection of regularity requires training and engages a form of NMDA receptor-mediated plasticity. The impact of stimulus exposure was assessed using a spinally mediated instrumental response, wherein spinally transected rats are given legshock whenever one hindlimb is extended. Over time, they learn to maintain the leg in a flexed position that minimizes net shock exposure. Prior exposure to 180-900 tailshocks given in a variable (unpredictable) manner inhibited this learning. A learning deficit was not observed when 900 tailshocks were applied using a fixed (predictable) spacing. Fixed-spaced stimulation did not have a divergent effect when fewer (180) shocks were presented, implying that the abstraction of temporal regularity required repeated exposure (training). Moreover, fixed-spaced stimulation both prevented and reversed the learning deficit. The protective effect of fixed-spaced shock lasted 48 h, and was prevented by pretreatment with the NMDA receptor antagonist MK-801. Administration of the protein synthesis inhibitor cycloheximide after training blocked the long-term effect. Inhibiting BDNF function, using TrkB-IgG, also eliminated the beneficial effect of fixed-spaced stimulation. The results suggest that spinal systems can detect regularity and that this type of stimulation promotes adaptive plasticity, which may foster recovery after spinal injury.
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Vichaya EG, Baumbauer KM, Carcoba LM, Grau JW, Meagher MW. Spinal glia modulate both adaptive and pathological processes. Brain Behav Immun 2009; 23:969-76. [PMID: 19435601 PMCID: PMC2749915 DOI: 10.1016/j.bbi.2009.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 05/05/2009] [Accepted: 05/05/2009] [Indexed: 12/16/2022] Open
Abstract
Recent research indicates that glial cells control complex functions within the nervous system. For example, it has been shown that glial cells contribute to the development of pathological pain, the process of long-term potentiation, and the formation of memories. These data suggest that glial cell activation exerts both adaptive and pathological effects within the CNS. To extend this line of work, the present study investigated the role of glia in spinal learning and spinal learning deficits using the spinal instrumental learning paradigm. In this paradigm rats are transected at the second thoracic vertebra (T2) and given shock to one hind limb whenever the limb is extended (controllable shock). Over time these subjects exhibit an increase in flexion duration that reduces net shock exposure. However, when spinalized rats are exposed to uncontrollable shock or inflammatory stimuli prior to testing with controllable shock, they exhibit a learning deficit. To examine the role of glial in this paradigm, spinal glial cells were pharmacologically inhibited through the use of fluorocitrate. Our results indicate that glia are involved in the acquisition, but not maintenance, of spinal learning. Furthermore, the data indicate that glial cells are involved in the development of both shock and inflammation-induced learning deficits. These findings are consistent with prior research indicating that glial cells are involved in both adaptive and pathological processes within the spinal cord.
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Affiliation(s)
| | | | | | | | - Mary W. Meagher
- Corresponding Author: Mary W. Meagher, Texas A&M University, MS 4235, College Station, TX 77843, , Phone: 979-845-2564, Fax: 979-458-4727
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26
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Pain and learning in a spinal system: contradictory outcomes from common origins. ACTA ACUST UNITED AC 2009; 61:124-43. [PMID: 19481111 DOI: 10.1016/j.brainresrev.2009.05.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 03/18/2009] [Accepted: 05/19/2009] [Indexed: 11/21/2022]
Abstract
The long-standing belief that the spinal cord serves merely as a conduit for information traveling to and from the brain is changing. Over the past decade, research has shown that the spinal cord is sensitive to response-outcome contingencies, demonstrating that spinal circuits have the capacity to modify behavior in response to differential environmental cues. If spinally transected rats are administered shock contingent on leg extension (controllable shock), they will maintain a flexion response that minimizes shock exposure. If, however, this contingency is broken, and shock is administered irrespective of limb position (uncontrollable shock), subjects cannot acquire the same flexion response. Interestingly, each of these treatments has a lasting effect on behavior; controllable shock enables future learning, while uncontrollable shock produces a long-lasting learning deficit. Here we suggest that the mechanisms underlying learning and the deficit may have evolved from machinery responsible for the spinal processing of noxious information. Experiments have shown that learning and the deficit require receptors and signaling cascades shown to be involved in central sensitization, including activation of NMDA and neurokinin receptors, as well as CaMKII. Further supporting this link between pain and learning, research has also shown that uncontrollable stimulation results in allodynia. Moreover, systemic inflammation and neonatal hindpaw injury each facilitate pain responding and undermine the ability of the spinal cord to support learning. These results suggest that the plasticity associated with learning and pain must be placed in a balance in order for adaptive outcomes to be observed.
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Group I metabotropic glutamate receptors control metaplasticity of spinal cord learning through a protein kinase C-dependent mechanism. J Neurosci 2009; 28:11939-49. [PMID: 19005059 DOI: 10.1523/jneurosci.3098-08.2008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Neurons within the spinal cord can support several forms of plasticity, including response-outcome (instrumental) learning. After a complete spinal transection, experimental subjects are capable of learning to hold the hindlimb in a flexed position (response) if shock (outcome) is delivered to the tibialis anterior muscle when the limb is extended. This response-contingent shock produces a robust learning that is mediated by ionotropic glutamate receptors (iGluRs). Exposure to nociceptive stimuli that are independent of limb position (e.g., uncontrollable shock; peripheral inflammation) produces a long-term (>24 h) inhibition of spinal learning. This inhibition of plasticity in spinal learning is itself a form of plasticity that requires iGluR activation and protein synthesis. Plasticity of plasticity (metaplasticity) in the CNS has been linked to group I metabotropic glutamate receptors (subtypes mGluR1 and mGluR5) and activation of protein kinase C (PKC). The present study explores the role of mGluRs and PKC in the metaplastic inhibition of spinal cord learning using a combination of behavioral, pharmacological, and biochemical techniques. Activation of group I mGluRs was found to be both necessary and sufficient for metaplastic inhibition of spinal learning. PKC was activated by stimuli that inhibit spinal learning, and inhibiting PKC activity restored the capacity for spinal learning. Finally, a PKC inhibitor blocked the metaplastic inhibition of spinal learning produced by a group I mGluR agonist. The data strongly suggest that group I mGluRs control metaplasticity of spinal learning through a PKC-dependent mechanism, providing a potential therapeutic target for promoting use-dependent plasticity after spinal cord injury.
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Baumbauer KM, Hoy KC, Huie JR, Hughes AJ, Woller SA, Puga DA, Setlow B, Grau JW. Timing in the absence of supraspinal input I: variable, but not fixed, spaced stimulation of the sciatic nerve undermines spinally-mediated instrumental learning. Neuroscience 2008; 155:1030-47. [PMID: 18674601 DOI: 10.1016/j.neuroscience.2008.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 06/27/2008] [Accepted: 07/02/2008] [Indexed: 10/21/2022]
Abstract
Rats with complete spinal transections are capable of acquiring a simple instrumentally trained response. If rats receive shock to one hind limb when the limb is extended (controllable shock), the spinal cord will learn to hold the leg in a flexed position that minimizes shock exposure. If shock is delivered irrespective of leg position, subjects do not exhibit an increase in flexion duration and subsequently fail to learn when tested with controllable shock (learning deficit). Just 6 min of variable intermittent shock produces a learning deficit that lasts 24 h. Evidence suggests that the neural mechanisms underlying the learning deficit may be related to those involved in other instances of spinal plasticity (e.g. windup, long-term potentiation). The present paper begins to explore these relations by demonstrating that direct stimulation of the sciatic nerve also impairs instrumental learning. Six minutes of electrical stimulation (mono- or biphasic direct current [DC]) of the sciatic nerve in spinally transected rats produced a voltage-dependent learning deficit that persisted for 24 h (experiments 1-2) and was dependent on C-fiber activation (experiment 7). Exposure to continuous stimulation did not produce a deficit, but intermittent burst or single pulse (as short as 0.1 ms) stimulation (delivered at a frequency of 0.5 Hz) did, irrespective of the pattern (fixed or variable) of stimulus delivery (experiments 3-6, 8). When the duration of stimulation was extended from 6 to 30 min, a surprising result emerged; shocks applied in a random (variable) fashion impaired subsequent learning whereas shocks given in a regular pattern (fixed spacing) did not (experiments 9-10). The results imply that spinal neurons are sensitive to temporal relations and that stimulation at regular intervals can have a restorative effect.
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Affiliation(s)
- K M Baumbauer
- Department of Psychology, Texas A&M University, College Station, TX 77843-4325, USA.
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29
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Abstract
Peripheral capsaicin treatment induces molecular changes that sensitize the responses of nociceptive neurons in the spinal dorsal horn. The current studies demonstrate that capsaicin also undermines the adaptive plasticity of the spinal cord, rendering the system incapable of learning a simple instrumental task. In these studies, male rats are transected at the second thoracic vertebra and are tested 24 to 48 hours later. During testing, subjects receive shock to one hindleg when it is extended (controllable stimulation). Rats quickly learn to maintain the leg in a flexed position. Rats that have been injected with capsaicin (1% or 3%) in the hindpaw fail to learn, even when tested on the leg contralateral to the injection. This learning deficit lasts at least 24 hours. Interestingly, training with controllable electrical stimulation prior to capsaicin administration protects the spinal cord against the maladaptive effects. Rats pretrained with controllable stimulation do not display a learning deficit or tactile allodynia. Moreover, controllable stimulation, combined with naltrexone, reverses the capsaicin-induced deficit. These data suggest that peripheral inflammation, accompanying spinal cord injuries, might have an adverse effect on recovery.
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Affiliation(s)
- Michelle A Hook
- Department of Psychology, Texas A&M University, College Station 77843-4235, USA.
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30
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Washburn SN, Maultsby ML, Puga DA, Grau JW. Opioid regulation of spinal cord plasticity: evidence the kappa-2 opioid receptor agonist GR89696 inhibits learning within the rat spinal cord. Neurobiol Learn Mem 2007; 89:1-16. [PMID: 17983769 DOI: 10.1016/j.nlm.2007.09.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Revised: 09/27/2007] [Accepted: 09/30/2007] [Indexed: 11/17/2022]
Abstract
Spinal cord neurons can support a simple form of instrumental learning. In this paradigm, rats completely transected at the second thoracic vertebra learn to minimize shock exposure by maintaining a hindlimb in a flexed position. Prior exposure to uncontrollable shock (shock independent of leg position) disrupts this learning. This learning deficit lasts for at least 24h and depends on the NMDA receptor. Intrathecal application of an opioid antagonist blocks the expression, but not the induction, of the learning deficit. A comparison of selective opioid antagonists implicated the kappa-opioid receptor. The present experiments further explore how opioids affect spinal instrumental learning using selective opioid agonists. Male Sprague-Dawley rats were given an intrathecal injection (30 nmol) of a kappa-1 (U69593), a kappa-2 (GR89696), a mu (DAMGO), or a delta opioid receptor agonist (DPDPE) 10 min prior to instrumental testing. Only the kappa-2 opioid receptor agonist GR89696 inhibited acquisition (Experiment 1). GR89696 inhibited learning in a dose-dependent fashion (Experiment 2), but had no effect on instrumental performance in previously trained subjects (Experiment 3). Pretreatment with an opioid antagonist (naltrexone) blocked the GR89696-induced learning deficit (Experiment 4). Administration of GR89696 did not produce a lasting impairment (Experiment 5) and a moderate dose of GR89696 (6 nmol) reduced the adverse consequences of uncontrollable nociceptive stimulation (Experiment 6). The results suggest that a kappa-2 opioid agonist inhibits neural modifications within the spinal cord.
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MESH Headings
- Adaptation, Physiological/drug effects
- Animals
- Association Learning/drug effects
- Association Learning/physiology
- Benzeneacetamides/pharmacology
- Conditioning, Operant/drug effects
- Conditioning, Operant/physiology
- Dose-Response Relationship, Drug
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- Male
- Neuronal Plasticity/drug effects
- Neuronal Plasticity/physiology
- Neurons/drug effects
- Neurons/metabolism
- Neurotransmitter Agents/pharmacology
- Piperazines/pharmacology
- Pyrrolidines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, kappa/metabolism
- Spinal Cord/cytology
- Spinal Cord/drug effects
- Spinal Cord/metabolism
- Spinal Cord Injuries/metabolism
- Thoracic Vertebrae
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Affiliation(s)
- Stephanie N Washburn
- Texas A&M University, Psychology Department, Mailstop 4235, College Station, TX 77843-4235, USA
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31
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Gómez-Pinilla F, Huie JR, Ying Z, Ferguson AR, Crown ED, Baumbauer KM, Edgerton VR, Grau JW. BDNF and learning: Evidence that instrumental training promotes learning within the spinal cord by up-regulating BDNF expression. Neuroscience 2007; 148:893-906. [PMID: 17719180 PMCID: PMC3225191 DOI: 10.1016/j.neuroscience.2007.05.051] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 04/24/2007] [Accepted: 05/22/2007] [Indexed: 10/22/2022]
Abstract
We have previously shown that the spinal cord is capable of learning a sensorimotor task in the absence of supraspinal input. Given the action of brain-derived neurotrophic factor (BDNF) on hippocampal learning, the current studies examined the role of BDNF in spinal learning. BDNF is a strong synaptic facilitator and, in association with other molecular signals (e.g. cAMP-response element binding protein (CREB), calcium/calmodulin activated protein kinase II (CaMKII) and synapsin I), important for learning. Spinally transected rats given shock to one hind leg when the leg extended beyond a selected threshold exhibited a progressive increase in flexion duration that minimized shock exposure, a simple form of instrumental learning. Instrumental learning resulted in elevated mRNA levels of BDNF, CaMKII, CREB, and synapsin I in the lumbar spinal cord region. The increases in BDNF, CREB, and CaMKII were proportional to the learning performance. Prior work has shown that instrumental training facilitates learning when subjects are tested on the contralateral leg with a higher response criterion. Pretreatment with the BDNF inhibitor TrkB-IgG blocked this facilitatory effect, as did the CaMKII inhibitor AIP. Intrathecal administration of BDNF facilitated learning when subjects were tested with a high response criterion. The findings indicate that instrumental training enables learning and elevates BDNF mRNA levels within the lumbar spinal cord. BDNF is both necessary, and sufficient, to produce the enabling effect.
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Affiliation(s)
- F Gómez-Pinilla
- Division of Neurosurgery, UCLA Brain Injury Research Center, USA.
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32
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Hook MA, Grau JW. An animal model of functional electrical stimulation: evidence that the central nervous system modulates the consequences of training. Spinal Cord 2007; 45:702-12. [PMID: 17700514 PMCID: PMC3222458 DOI: 10.1038/sj.sc.3102096] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
STUDY DESIGN Review of how spinal neurons can modulate the consequences of functional electrical stimulation (FES) in an animal model. METHODS Spinal effects of FES are examined in male Sprague-Dawley rats transected at the second thoracic vertebra. The rats are exposed to FES training 24-48 h after surgery. Experimental manipulations of stimulation parameters, combined with physiological and pharmacological procedures, are used to examine the potential role of spinal neurons. RESULTS The isolated spinal cord is inherently capable of learning the response-outcome relations imposed in FES training contingencies. Adaptive behavioral modifications are observed when an outcome (electrical stimulation) is contingent on a behavioral response. In contrast, a lack of correlation between the response and outcome in training produces a learning deficit in the spinal cord, rendering it incapable of adaptive learning for up to 48 h. The N-methyl-D-aspartic acid receptor appears to mediate both the adaptive plasticity and loss of plasticity, seen in this spinal model. CONCLUSION The behavioral effects observed with FES therapies are not simply due to the direct (motor) consequences of stimulation elicited by the activation of efferent motor neurons and/or selected muscles. FES training has the capacity to shape inherent spinal circuits and to produce a long-lasting behavioral modification. Further understanding of the spinal mechanisms underlying adaptive behavioral modification will be integral for establishing functional neural connections in a regenerating spinal system.
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Affiliation(s)
- M A Hook
- Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA
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33
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Young EE, Baumbauer KM, Elliot A, Joynes RL. Lipopolysaccharide induces a spinal learning deficit that is blocked by IL-1 receptor antagonism. Brain Behav Immun 2007; 21:748-57. [PMID: 17382514 DOI: 10.1016/j.bbi.2007.02.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Revised: 02/04/2007] [Accepted: 02/06/2007] [Indexed: 10/23/2022] Open
Abstract
Previous studies have shown that spinal neurons are capable of supporting a form of instrumental conditioning. Subjects receiving a spinal transection will learn to maintain a flexion response after exposure to shock contingent on leg position. In contrast, subjects receiving shock irrespective of leg position will not show increased flexion duration. Activation of the immune system has deleterious effects on learning in intact animals, but the impact of immune system activation on learning spinal animals is not known. We found that a large dose of i.p. LPS (1.0mg/kg) significantly disrupted the acquisition of the instrumental flexion response. The LPS-induced learning deficit was not prevented by preexposure to contingent shock (i.e. immunization) (Experiment 2). Co-administration of the iNOS inhibitor L-NIL (0.1, 1.0 and 10.0 microg/microL) failed to block the deficit (Experiment 3). Co-administration of an IL-1 receptor antagonist (r-metHuIL-1ra [10.0, 30.0 and 100.0 microg/microL) prevented the LPS-induced learning deficit when given in a dose of 100.0 microg/microL(i.t.) only (Experiment 4). Findings indicate a role for spinal IL-1 in the decreased plasticity following LPS administration.
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34
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Washburn SN, Patton BC, Ferguson AR, Hudson KL, Grau JW. Exposure to intermittent nociceptive stimulation under pentobarbital anesthesia disrupts spinal cord function in rats. Psychopharmacology (Berl) 2007; 192:243-52. [PMID: 17297638 PMCID: PMC3222461 DOI: 10.1007/s00213-007-0707-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 01/08/2007] [Indexed: 10/23/2022]
Abstract
RATIONALE Spinal cord plasticity can be assessed in spinal rats using an instrumental learning paradigm in which subjects learn an instrumental response, hindlimb flexion, to minimize shock exposure. Prior exposure to uncontrollable intermittent stimulation blocks learning in spinal rats but has no effect if given before spinal transection, suggesting that supraspinal systems modulate nociceptive input to the spinal cord, rendering it less susceptible to the detrimental consequences of uncontrollable stimulation. OBJECTIVE The present study examines whether disrupting brain function with pentobarbital blocks descending inhibitory systems that normally modulate nociceptive input, making the spinal cord more sensitive to the adverse effect of uncontrollable intermittent stimulation. MATERIALS AND METHODS Male Sprague-Dawley rats received uncontrollable intermittent stimulation during pentobarbital anesthesia after (experiment 1) or before (experiment 2) spinal cord transection. They were then tested for instrumental learning at a later time point. Experiment 3 examined whether these manipulations affected nociceptive (thermal) thresholds. RESULTS Experiment 1 showed that pentobarbital had no effect on the induction of the learning deficit after spinal cord transection. Experiment 2 showed that intact rats anesthetized during uncontrollable intermittent stimulation failed to learn when later transected and tested for instrumental learning. Experiment 3 found that uncontrollable intermittent stimulation induced an antinociception in intact subjects that was blocked by pentobarbital. CONCLUSIONS The results suggest a surgical dose of pentobarbital (50 mg/kg) suppresses supraspinal (experiment 2) but not spinal (experiment 1) systems that modulate nociceptive input to the spinal cord by blocking the antinociception that is induced by this input (experiment 3).
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Affiliation(s)
- Stephanie N Washburn
- Psychology Department, Texas A&M University, College Station, TX 77843-4235, USA.
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35
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Grau JW, Crown ED, Ferguson AR, Washburn SN, Hook MA, Miranda RC. Instrumental learning within the spinal cord: underlying mechanisms and implications for recovery after injury. ACTA ACUST UNITED AC 2007; 5:191-239. [PMID: 17099112 DOI: 10.1177/1534582306289738] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Using spinally transected rats, research has shown that neurons within the L4-S2 spinal cord are sensitive to response-outcome (instrumental) relations. This learning depends on a form of N-methyl-D-aspartate (NMDA)-mediated plasticity. Instrumental training enables subsequent learning, and this effect has been linked to the expression of brain-derived neurotrophic factor. Rats given uncontrollable stimulation later exhibit impaired instrumental learning, and this deficit lasts up to 48 hr. The induction of the deficit can be blocked by prior training with controllable shock, the concurrent presentation of a tonic stimulus that induces antinociception, or pretreatment with an NMDA or gamma-aminobutyric acid-A antagonist. The expression of the deficit depends on a kappa opioid. Uncontrollable stimulation enhances mechanical reactivity (allodynia), and treatments that induce allodynia (e.g., inflammation) inhibit learning. In intact animals, descending serotonergic neurons exert a protective effect that blocks the adverse consequences of uncontrollable stimulation. Uncontrollable, but not controllable, stimulation impairs the recovery of function after a contusion injury.
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Affiliation(s)
- James W Grau
- Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA.
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36
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Ferguson AR, Crown ED, Grau JW. Nociceptive plasticity inhibits adaptive learning in the spinal cord. Neuroscience 2006; 141:421-31. [PMID: 16678969 DOI: 10.1016/j.neuroscience.2006.03.029] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2005] [Revised: 03/08/2006] [Accepted: 03/18/2006] [Indexed: 11/29/2022]
Abstract
Spinal plasticity is known to play a role in central neurogenic pain. Over the last 100 years researchers have found that the spinal cord is also capable of supporting other forms of plasticity including several forms of learning. To study instrumental (response-outcome) learning in the spinal cord, we use a preparation in which spinally transected rats are given shock to the hind leg when the leg is extended. The spinal cord rapidly learns to hold the leg in a flexed position when given this controllable shock. However, if shock is independent of leg position (uncontrollable shock), subjects fail to learn. Uncontrollable shock also impairs future learning. As little as 6 min of uncontrollable shock to either the leg or the tail generates a learning deficit that lasts up to 48 h. Recent data suggest links between the learning deficit and the sensitization of pain circuits associated with inflammation or injury (central sensitization). Here, we explored whether central sensitization and the spinal learning deficit share pharmacological and behavioral features. Central sensitization enhances reactivity to mechanical stimulation (allodynia) and depends on the N-methyl-d-aspartate receptor (NMDAR). The uncontrollable shock stimulus that generates a learning deficit produced a tactile allodynia (Exp. 1) and administration of the NMDAR antagonist MK-801 blocked induction of the learning deficit (Exp. 2). Finally, a treatment known to induce central sensitization, intradermal carrageenan, produced a spinal learning deficit (Exp. 3). The findings suggest that the induction of central sensitization inhibits selective response modifications.
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Affiliation(s)
- A R Ferguson
- Department of Neuroscience, The Ohio State University, 333 West 10th Avenue, Columbus, OH 43210, USA.
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Liu GT, Ferguson AR, Crown ED, Bopp AC, Miranda RC, Grau JW. Instrumental learning within the rat spinal cord: localization of the essential neural circuit. Behav Neurosci 2005; 119:538-47. [PMID: 15839800 DOI: 10.1037/0735-7044.119.2.538] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Following spinal transection of the upper thoracic spinal cord, male Sprague-Dawley rats given legshock whenever a hindlimb is extended learn to maintain the leg in a flexed position. The region of the cord that mediates this instrumental learning was isolated using neuroanatomical tracing, localized infusion of lidocaine, and surgical transections. DiI and Fluoro-Gold microinjection at the site of shock application labeled motor neuron bodies of lamina IX in the lower lumbar region. Local application of the Na-super++ channel blocker lidocaine disrupted learning when it was applied over a region extending from the lower lumbar (L3) to upper sacral (S2) cord. The drug had no effect rostral or caudal to this region. Surgical transections as low as L4 had no effect on learning. Learning also survived a dual transection at L4 and S3, but not L4 and S2. The results suggest that the essential neural circuit lies between L4 and S3.
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Affiliation(s)
- Grace T Liu
- Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA
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